Nearly 2000 prescription pills have been seized by Customs and examined by Medsafe last week, as part of a worldwide Interpol operation to clamp down on illegal and counterfeit medications.

New Zealand was one of more than 60 countries taking part in Operation Pangea V - aimed at disrupting the criminal networks and snuffing out the internet drug lords behind the illicit online sale of medicines.

The operation, carried out over a week from last Tuesday, saw Customs seize 190 packages containing medications brought to New Zealand through the International Mail Centre.

The packages were then assessed by drug safety authority Medsafe, and a 124 of those required further investigation.

Medsafe Group Manager Stewart Jessamine said it could be quite dangerous purchasing prescription medicines online "because you cannot be sure the medicines supplied will meet the New Zealand laws assuring quality, safety and effectiveness.

"Prescription medicines are not ordinary commodities. They are potent substances and as such should only be used following a consultation with a doctor in New Zealand," he said.

"If you've got a serious illness there are no short cuts unfortunately, you have got to see your doctor."

Jessamine said many medications were also marketed as herbal remedies, but actually contained prescription medications which if mixed with other medications a person might be taking, had the potential to be fatal.

The parcels, which came from 21 different countries, contained more than 1890 tablets or capsules - the most common being treatments for erectile dysfunction.

The Ministry of Health said antibiotics and insomnia pills were the next most common drugs to be brought illegally into New Zealand. Jessamine said while over the course of that week they were cooperating internationally, it was "really just business as usual" for New Zealand authorities.

Between 12,000 - 14,000 parcels were intercepted on average throughout the year.

The 124 packages that were seized by Medsafe over the duration of the operation often contained more than one type of prescription medicine.

Last year's operation, Pangea IV, saw more than 2.4 million counterfeit drugs confiscated globally worth more than NZ$76 million.

Jessamine said it was important that any patient wanting to buy prescription medicines consulted with their doctor.

He said it was vital patients received the correct information on potential side effects, interactions with other medicines and the appropriate dosage.

Over the period of this year's operation Customs and Medsafe heightened their screening process, but as a matter of course all prescription medicines imported in New Zealand are referred to Medsafe to ensure they are being brought in legally.

Those who had tried to import medications into New Zealand were given the opportunity to get a prescription from a doctor in New Zealand before their drugs were handed to them.

"In those cases the patients are given a letter from us, basically saying the patient has tried to purchase medications online - 'we don't know where they have been made, or in fact whether they contain only what they say they do, are you willing to write a prescription for this?'"

Jessamine said doctors in about 30 per cent of those cases wrote prescriptions for online bought medication.